Why don't we see steering knobs anymore?

a href="http://www.google.com/search?q=%22steering+wheel+knob%22&hl=en&num=10&lr=&ft=i&cr=&safe=off&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&biw=1600&bih=1115" rel="nofollow"http://www.google.com/search?q=%22steeri…/a